Hydrogen-cooled generators are often used by power utilities for generating electricity. Typically contaminants in the hydrogen cooling gas hydrogen-cooled generators need to be removed.
FIG. 1 diagrammatically illustrates a prior art “open” regenerative system 100 available from Environment One of Niskayuna, N.Y., for drying hydrogen gas used in a hydrogen-cooled generator. System 100 is configured as a dual-chamber system operable to continuously dry and recirculate generator cooling gas even when the generator is on turning gear. The system includes a first drying tower or column 110 and a second tower or column 130. Each of the columns includes a housing 112 and 132, a heater 114 and 134, and a desiccant 116 and 136, respectively. During normal operation, hydrogen gas from the hydrogen-cooled generator enters the upper end of column 110, passes through desiccant 116 to the lower end of the column, and the dried hydrogen gas is returned to the hydrogen-cooled generator. Generally during normal operation of column 110 for drying a supply of hydrogen gas from the hydrogen-cooled generator, heater 114 of column 110 is not activated and a valve 180 is closed so that no flow of dry hydrogen gas supplied via conduits 162 and 164 to second column 130.
As shown in FIG. 1, system 100 is configured for drying hydrogen gas from the hydrogen-cooled generator, and at the same time, operable to regenerate saturated desiccant 136 in second column 130. In particular, valves or manifolds 150 and 160 operably connect first column 110 for drying hydrogen gas from the hydrogen-cooled generator. At the same time, valves or manifolds 150 and 160 operably connect second column 130 for regeneration of desiccant 136 in second column 130. In the configuration for regenerating second column 130, a continuous supply of dried hydrogen gas from first column 110 is also supplied to second column 130 via valve or manifold 160 and operable conduits 162 and 164. During the process of regenerating the desiccant in the second column, heater 134 is turned on to heat the desiccant to turn the water in the desiccant into steam which steam is carried along with the supply of dry hydrogen from conduit 164 and exhausted out of the second column, via conduits 172 and 174 to a vent 176. Once the desiccant in second column is dried, heater 134 is turned off and valve 180 is closed. At an appropriate time, valves or manifolds 150 and 160 may be operated to operably connect the second column for drying the hydrogen gas in the hydrogen-cooled generator, and at the same time, regenerate the desiccant in the first column. The column regeneration is automated via a controller 190 and takes place based on programmable inlet and outlet dew point levels. The heater heats the desiccant to about 300 degrees Celsius, and the regenerative process takes about 2 hours to about 3 hours.
FIG. 2 diagrammatically illustrates a prior art “closed” regenerative system 200 available from Lectrodryer, L.L.C. of Richmond, Ky. under the model name BAC-50 for drying hydrogen gas used in a hydrogen-cooled generator. System 200 is configured as a continuous operating automatic twin tower. The system includes a first drying tower or column 210 and a second tower or column 230. Each of the columns includes a housing 212 and 232, a heater 214 and 234, and a desiccant therein, respectively. During normal operation, hydrogen gas (illustrated in black arrows in FIG. 2) from the hydrogen-cooled generator enters the lower end of column 210, passes through the desiccant to the upper end of the column, and the dried hydrogen gas is returned to the hydrogen-cooled generator. In the closed regenerative system of FIG. 2, a closed loop of hydrogen gas (illustrated in white arrows in FIG. 2) circulates while heater 234 is turned on to turn the water in the desiccant in column 230 into steam. The closed loop circulation of hydrogen gas carries the steam out of the column. A cooler 220 then cools the steam and hydrogen gas, via cooling water or other refrigerant, to condense the steam into water which condensed water is removed in a trap 250 and exhausted out via a drain 260.
There is a need for further methods and systems for drying hydrogen gas used in hydrogen-cooled generators.